Everything that you added into the article seemed like relevant information to me and helped flesh out a little the organization, so that was very good. You did not add any biased information or portray any bias. There is not too much information on the topic anyway so I do not think anything is underrepresented. Your citation link worked for me. I did not think any information was out of date looking through your source and it is a reliable one.
Suggestions:
Honestly there is not really anything wrong with what you have. Maybe find another secondary source if you can to bolster that aspect of the article. I do not know how much information is out their for your topic so I do not know the feasibility of that suggestion. Personally, I find the original article not formatted in a way I like. It is not good look at. Personally I would make a section with a subheading saying "Members (from whenever - present) and then format it like that. I do not know how to add a little box to te side that is seen in most wikipedia articles at the top of the page with quick information, but if that could be added that would be great. I think those things would help it look better. Those are just personal suggestions and preferences so take those as you may! Otherwise, good work.